Filled asphalt and asphalt coated roofing compositions



Patented May 21, 1946 ASPHALT AND ASPHALT COATED ROOFING COLIBOSITION SFrancis L. Mark, Redondo Beach, Calif.

Serial No. 460,920

No Drawing. Application ctober5, 1942,

4 clams. Thi invention relates to filled asphaltic cements and to filledasphaltic coating composition employing balanced mixtures of finelydivided (c1. roe-281) mineral matter, such as fine mineral dust, and

diatomaceous earths. Filled asphalt containing mineral dust, such asrock dust and diatomaceous earths have been employed during the past forvarious uses. It has been observed that the addition of diatomaceousearth to steam refined asphalts has the effect of imparting to suchasphalt some of the properties of air-blown asphalt, the addition 01'the diatomaceous earth increasing the softening point and lowering thepenetration of steam refined asphalt. The addition of diatomaceous earthalso has the efiect of increasing the tensile strength of steam refinedasphalt. However,'such mixtures of asphalt and diatomaceous earth do nothave the pliability ofairin diameter. when this un is unwound at lowtemperatures transverse cracks appear inthe coating and often carryclear through the base felt itself. As a result, the roofing cap sheetdisintegrates -,and allows water to enter the underlying roof structure.This may result in leaks and in moisture blisters on the surface.

In order to limit this cold weather cracking it has been necessary inthe past to use relatively soft. asphalts. This was made particularlyimperative by the fact that the filler added to the asphalt had theeffect or actually increasing the brittleness of the asphalt. Themanufacturer'of asphalt roofing was'then on the horns of a dilemma. Hecould have asphaltic roofing which would not run and excessively softenat the high temperatures to which the roofing might be blown asphaltmixtures and. at low temperatures are brittle. This brittleness of suchasphalts has excluded them from use in one of the most important fieldsof asphalt application, that is in prepared roofing.

Prepared roofing, whether of the rolled sheet type or the shingle type.is prepared by saturating felted material with a saturating asphalt,after which the asphalt saturated sheet is coated with a filled typeasphalt material. The coated asphalt may be sprinkled with rock granuleswhile the asphalt is softand the granules are pressed-into the asphalt,

The type of asphalt which has been employed for thiscoating purpose hasbeen an air-blown asphalt because the steam blown asphalts, even thoughthey are filled, are too. brittle at low tem "v peratures and too softat high temperatures.

Fillers are employed in the asphalt for'the purexposed in the summertimeby using an asphalt of a relatively high melting point andaddingsufilcient filler and as a result sufier the cracks and shatteringeffect whichfollow from the brittleness of such mixtures at lowtemperatures. He could use a soft asphalt and limit his filler contentto obtain proper pliability at low temperatures, but suffer theconsequences of a running asphalt at high temperatures. phalts at hightemperatures becomedisplaced when asphalt roofings are positioned at anyangle and since the granules of aggregate employed as a coating becomedisplaced, due to the softness of the asphalt, such'asphalt roofings areimpractical.

facturer was forced to sufier the consequences of lack of lowtemperature pliability of his filled asa phalt type of coating.

pose of stiffening the. asphalt and rendering it less the roofing may beexposed in construction or use. One of the most serious of thesedifiiculties is the cracking or shattering or the asphalt at lowtemperatures. Thus the asphalt coated roofing may not be laid attemperature much below about to.60 F. Shingles when laid at thistemperature are shattered when nails are driven through the shingles.Rolled roofing is wound into rolls usually on a mandrel core or 4" to 5"While this typ of coatsceptible to temperature change. The minera I havenow made the discovery that diatomaceous earth when used in proportionedmixes with mineral dust in oxidized asphalt givesa balanced mix whichremoves the manufacturer from the horns of the dilemma. It gives the,high temperature stability together with the low tempera-- turepliability.

Diatomaceous earth, as employed in this in-' vention, produces a markedincrease in the softening point of the asphalt. Less than ten per centof this material when used-with mineral dust in proper-proportion willraisethe softening point of a blown asphalt from abeut; F. to 230resulting in a coating of greatly improved pliability and higher tensilestrength and resistance -to Since such as-v Since the latterconsiderations are more im-l portant and in many cases controlling, theinanu- .my invention is given by and to free mixture of water.

. is then added. The diatomaceous earth has the 2 the pliability of theasphalt has permitted me to make roofing material which may be handledas low as 5 F. without any cracking. In unrolling such a rolled roofingno cracking has been apparent, even down to' the last portion withsharpest curvature. Repeated flexing of this material has shown that itis entirely pliable so that it may be handled without cracking. Whenusing this material on shingles it may be-nailed at temperatures wellbelow freezing without shattering.

Asphalt roofing may contain small amounts of water even though theasphalt is carried to 500 F. in its preparation. It is present due toabsorption in the felted sheet and may be present under the roofing laidover an old roof or it may enter through seams. When this moistureexpands into vapor it causes blistering of the surface and a destructionof the coating. I have found that the addition of this diatomaceousearthin proper proportion, mixed with minera filler material gives a toughersurface which prevents blistering. This arises from the fact that;

the diatomaceous earth will increase the tensile strength of theasphalt.

The ability of the .diatomaceous earth to raise the melting point whileimproving the low temperature pliability has permitted me to use lowersoftening point oxidized asphalts and thus I have phalts because I havebeen able to impart this high temperature stability by the use ordiatomaceous earth. This lower-softening point has improved the adhesiveproperties of the asphalt mix and I have been able to overcome thetendency of the asphalt to run and the granules to be displaced at hightemperatures.

' The diatomaceousearth also results asphalt of improved weatheringproperties when subjected to the standard Weatherometefl test in whichthe asphalt was subject to rays at 140 F. and frozen at F. in repeatedoperations. The diatomaceous earth filled asphalts of my invention-showan improvement in weathering characteristics showing a resistance tofailure of one-third or more. In other words, they may be exposed to theabove treatment for a 3, /a% greater period than the rock dust filledtype of oxidized asphalt before failure occurs. V

The following exampleof one embodiment of not for the purpose oflimiting my invention:

In making the filled asphalt of my invention,

. I employ an air-blown asphalt having a ball and. ring softeningrpointof 190 to 205 F. The

phalt is heated to a astemperature of about 350" to use kilndrieddiatomaceous earth that is uncalcined material having a water content ofabout 6% or less.

, centrifuge tube which is filled to the 1,5 centiother proportions andspecifications will give a for rolled roofing.

int. filled ultra-violet way of illustration and I or higher, sumcientto impart fluidity to theasphalt. To'this asphalt'is added mineralfiller of the conventional type, to-wit: rcckdust, pulverized limestone,fine silica sand. round mica, talc, volcanic ash, clays, groundasbestos, powdered meter mark. The tube is whirled at 1800 revolutions.per minute and the volum occupied by the diatomaceous earth is read andconverted into pounds per cubic foot.

The asphalt and diatomaceous earth and powdered mineral filler areproportioned to give the following properties. The'ball and ring meltingpoint should be 210 F. or better. The viscosity of the mixture when readat 360 by the Brookfield Viscosimeter should be in the range of about5,000 to 20,000 centipoises'. The penetration, when measured on thestandard penetrometer, according to ASTM specifications, employing gramsfor five seconds at 77 F. should range from about 1.2 to 1.7millimeters. I proportion the. asphalt, rock dust, and diatomaceousearth to obtain the above specifications. While useful result and I donot desire to be limited to the'illustration of my preferred embodiment,I have found that the above limits give a highly advantageous resultwhen employed as a coating In the following tabla which illustratesvarious examples of compositions employed, the symbol S. P. representsthe softening point of the asphalt.

The symbol P. D. represents paving dust and D represents diatomaceousearth and B. 8: R. standsfor ball and ring softening point. Table 1Asphalt 55% of S. P. 62% Of 195 S. P.

Filler 39% P. D.,'6% D. 8% D.,30% P. D. Softening point 230 219 vPenetration-77 F. v 1.7 1.7 ViS. at 360 9,200 C. 5,000 C. P.

Table 2 0 Percent Percent Softening Penetra- Perceut a i at? at? as 11100 195- 26 55 7.6 31.4 229 16 55 c 22s 1c In choosing the diatomaceousearth to be employed in my composition, by a proper selection of thetype of. diatoms which I use I have been able to obtain a highlyimproved result in increasing the melting point and tensile strength aswell as the pliability of filled asphalt. This improvement in theseproperties is ofgeneral utility ploying' diatomaceous earth, such as inpipe line coating, road'construction and in all places where filledasphalt has been employed asan asphaltic shells, slate flour.Diatomaceous earth is also i added. I find that I obtain superiorresults by first dispersing the diatomaceous earth in the asphalt,agitating the. mixture to ensure dispersal The mineral filler mineralfiller to prevent undue settling. I prefer,

cement. There are over 10,000 different types ,0! diatoms. Of thesetypes are those whose length is markedlygreater than their width. Theround or disc shaped diatoms,

For best results, diatomaceous earthshould have a wet density ofabout 18or lesspounds per cubic foot.

I have discoveredthat in filled asphalts em- I I there is one class ofdiatoms which is termed the elongated type.

The type of diatoms which are here'referred to their dimensions oflength and width nearly equal, do not have as great an effect. This typeof diatom may be employed, but must be used in larger amounts nor dothey have the eflect of improving the low temperature pliability and thetensile strength that is obtained with the elongated type. Theseelongated forms are characterized by skeletons which are wide and thinor long and narrow. These elongated" diatoms are to'be contrasted withthe smallheavy walled type. This classification is well understood inthis art. See 1, 2, 3, and 9, and 12 to 18 of Diatomaceous Earth byCalvert, A. C. S. Monogram Series 52, Edition of 1930.? Some examples ofthe elongated type appear in Fig. 16. Examples of the round type appearin Fig.13. I have found that when employing these elongated diatoms Imay obtain a better result in improvement of tensile strength and lowtemperature pliability than when employing diatoms whose dimensions oflength and breadth more closely approach each other, as in the case ofthe round type of diatom.

It is to be understood that the foregoing examples are for purposes ofillustration and are not to be considered as limiting of the invention.Various changes and modifications may be made therein without departingfrom the spirit of the appended claims.

I claim: 1. A filled asphalt comprising an oxidized asphalt having abail and ring softening point or about 190 to about 205 F. and mineralfiller and kiln dried diatomaceous earth whose diatoms, in preponderantproportion, are of the elongated type. having a wet density of less thanabout 18, said mixture of asphalt, filler, and diatomaceous earth havinga ball and ring softening point of at least 210 F., and higher than saidoxidized asphalt, a viscosity of about 5,000 to 20,000 centipoi ses at360 1". and a penetration of 1.2 to 1.7 millimeters when measured at 7'11"., employing loo-gram weight for five seconds.

2. A filled asphalt comprising an oxidized asphalt having a ball andring softening point of about 190 to about 205' I". and mineralfillerand kiln dried diatomaceous earth having less 5 than about 6%moisture, said mixture of asphalt,

filler and diatomaceous earth, whose diatoms in preponderant proportionare of the elongated type, having a ball and ring softening point of atleast 210 F. and higher than said oxidized l0 asphalt, a viscosity ofabout 5,000 to 20,000 centi-- poises at 360 F. and a penetration of 1.2to 1.7

100-gram weight for five seconds.

3. Prepared roofing comprising-sheet material millimeters when measuredat 77 F., employing coated with a filled asphalt comprising an oxidizedasphalt having a ball and ring softening point of about 190 to about 205F. and mineral filler and kiln dried diatomaceous earth whose diatoms,in preponderant proportions, are of the go elongated species, having awet density of less than about 18, said mixture of asphalt, filler anddiatomaoeous-earth having a ball and ring softening point of 210 F. orbetten-and higher than said oxidized asphalt, a viscosity of about 5,000to 20,000 centipoises at 360? F. and a penetration of 1.2 to 1.7millimeters when measured at 77 F., employing IOU-gram weight for fiveseconds.

' 4. Prepared roofing comprising sheet material coated with a filledasphalt comprising an oxiso dized asphalt having a ball and ringsoftening point of about 190 to about 205 F. and mineral filler and kilndried diatomaceous earth whose diatoms, in preponderant proportions, areof elongated species, having less than about 6% moisture, said mixtureof asphalt, filler and di-- atomaceous earth having a ball and ringsoftening' point of 1 210 1". or better, and higher than said oxidizedasphalt. a viscosity of about 5,000 to 20,000 centipoises at 380? F. anda penetration of 40 1.2 to 1.! millimeters when measured at 77 1'2,

employing -gram weight for five seconds.

